The constitutive equations for the flow behavior of a commercial 0.34 pct C-1.5 pct Mn-0.7 pct Si-0.083 pct V-0.018 pct Ti microalloyed steel were determined. For this purpose, uniaxial hot compression tests were carried out over a wide range of strain rates (10 Ϫ4 to 10 s Ϫ1 ) and temperatures (1123 to 1423 K). In combination with models developed in the literature, the experimental results permit the flow stress of the present steel to be predicted within ‫5ע‬ pct. It is shown that the classical constitutive equations must be modified to take the grain size into account, particularly when the latter is below 30 m.

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Abstract.Research was conducted to investigate the potential for consolidating titanium powder using high-pressure torsion (HPT) at room temperature. The nanostructured samples processed by HPT were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM).The results show there is a significant refinement of the Ti powder and it consolidates into bulk nanostructured titanium with a mean grain size estimated by TEM as ~200-300 nm and a mean crystallite size measured by XRD as ~20-30 nm. Microhardness measurements and tensile testing show high strength and low ductility after consolidation under a pressure of 6.0 GPa for 5 revolutions. Additional short annealing at a temperature of 300°C for 10 minutes leads to a significant enhancement in ductility while maintaining the high strength.

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